"please explain using java"

very detail explanations

1. Given int variables k and total that have already been declared, use a for loop to compute the sum of the squares of the first 50 counting numbers, and store this value in total. Thus your code should put 1*1 + 2*2 + 3*3 +... + 49*49 + 50*50 into total. Use no variables other than k and total.

2. Given an int variable k that has already been declared, use a for loop to print a single line consisting of 97 asterisks. Use no variables other than k.

3. Given an int variable n that has already been declared and initialized to a positive value, and another int variable j that has already been declared, use a for loop to print a single line consisting of n asterisks. Thus if n contains 5, five asterisks will be printed. Use no variables other than n and j.

4. Write a for loop that prints the integers 0 through 39, separated by spaces.